Hybrid automatic repeat request (HARQ), in which automatic repeat request (ARQ) disclosed in Non-patent Documents 1 and 2 and error correction coding such as turbo coding are combined, is an example of an error control technique in communication systems. HARQ is a technique by which a receiver requests a transmitter to perform retransmission when detecting an error from a received signal, and performs a decoding process on a combined signal of a signal received again and a previously received signal. In particular, since redundant bits are divided and sequentially retransmitted bit by bit in incremental redundancy (IR) as one type of HARQ, it is possible to decrease the coding rate and enhance the error correction capability according to an increase of the number of retransmissions.
On the other hand, a multi carrier-code division multiplexing (MC-CDM) scheme, a spread-orthogonal frequency division multiplexing (spread-OFDM) scheme, and the like are examples of combinations of a multi-carrier transmission scheme such as orthogonal frequency division multiplexing (OFDM) and a code division multiplexing (CDM) scheme. In these schemes, good characteristics are obtained under multipath fading environments by arranging coded and spreading code-multiplied data over subcarriers and acquiring the effect of frequency diversity. Multi-code interference (MCI) due to the destruction of orthogonality between spreading codes upon code multiplexing occurs and becomes the cause of characteristic degradation.
As a technique for solving this problem, for example, a successive interference canceller (SIC) is disclosed in Non-patent Documents 3 and 4. The SIC disclosed in Non-patent Documents 3 and 4 uses a technique of performing signal detection by performing despreading, demodulation, and decoding in order from a channel signal of which received signal power or a received signal to interference plus noise power ratio (SINR) is high among code-multiplexed received signals, obtaining a determination signal of an information symbol, and subtracting an interference signal replica (undesired signal) created using a determination result thereof from a received signal. By iterating this procedure, it is possible to accurately remove a signal serving as an interference signal other than a desired code channel and suppress characteristic degradation due to the destruction of orthogonality between spreading code sequences.
[Related Art Document]
[Non-patent Document]
    [Non-patent Document 1] D. Chase, “Code combining-A maximum likelihood decoding approach for combining and arbitrary number of noisy packets” IEEE Trans. Commun., vol. COM-33, pp. 385-393, May 1985.    [Non-patent Document 2] J. Hagenauer, “Rate-compatible punctured convolutional codes (RCPC codes) and their application”, IEEE Trans. Commun., vol. 36, pp. 389-400, April 1988.    [Non-patent Document 3] Ishihara, Takeda, and Adachi, “DS-CDMA Frequency Domain MAI Canceller,” The Institute of Electronics, Information and Communication Engineers, technical report RCS 2004-316, January 2005.    [Non-patent Document 4] Akita, Suyama, Fukawa, and Suzuki, “Interference Canceller in Downlink Using Transmission Power Control of MC-CDMA,” The Institute of Electronics, Information and Communication Engineers, technical report RCS 2002-35, April 2002.